The material was fed by gravity in the early extruders. Due to the backpressure at the outlet, this feeding method often led to material accumulation at the inlet when material was oversupplied and material slippage when material was undersupplied, resulting in low efficiency and low stability of the extruder. Thereafter, a new extruder was proposed which had a lateral pressure roller being provided at the inlet, and material was fed by means of this roller. This feeding method alleviated the problems of the material accumulation and slippage, however, due to the structure of the feeding apparatus, this method led to material leakage and material being forced into the bearings on both ends of the lateral pressure roller and thus failure of the roller. Although the currently used feeding method using a lateral pressure roller can improve the efficiency and stability of the extruder, the feeding apparatus has a high rate of failure, complicated structure and is difficult to manufacture. In order to overcome above drawbacks and improve the existing feeding method, the persons skilled in the art have proposed that the axial channels and spiral channels used in the feeding apparatus of plastic extruder be introduced into cold feed extruder, but no ideal results have been obtained therefrom. As a result, cold feed extruder still uses lateral pressure roller for the feeding of the material.